In general, an image processing software usually comes with a layer processing function that allows each image to be resided at a layer all the time as shown in FIG. 1, and thus users usually need to create a layer 111, 121 or add a layer before processing (including editing or composing) an image 110, 120 in a file, and a canvas 130 is situated at the lowest layer of all layers 111, 121 but the canvas 130 is not a layer by itself. Therefore, the layers 111, 121 are similar to a stack of transparent films, and the layers 111, 121 can help a user to organize the images 110, 120 in a file, so that the user can edit the image 110 on the layer 111 without affecting the image 120 on the other layer 121. If the layer 111 contains no image 110, then the user will be able to see the image 120 on the layer 121 through the layer 111. In addition, a user can view the stack sequence of the layers and images on a layer display panel provided by different image processing software, and such stack sequence is also the sequence of images appeared in the document. In general, various different image processing software stack the layers according to such sequence, and the later produced layer is placed at the top of the stack, and the stack sequence determines how to stack an image of a layer on an image of another layer, such that users can rearrange the sequence of layers and images through a control interface of the image processing software to change the content of the images in a file.
Referring to FIG. 2 for an image processing software called “Photoshop” available in the market, a user can create two images 210, 220 on two separate layers from a layer display panel provided by the image processing software, if the user wants to compose two images 210, 220. A composed image 310 is created as shown in FIG. 3, after the size and position of each image 210, 220 are adjusted according to the user's requirements. Referring to FIG. 4, a user can click on an [Add Mask] button 450 to create a mask 440 for a first image 410 on the first layer 411, if the user wants to edit the first image 410 on the layer display panel 400. In FIG. 5, a brush tool 471 is selected from a tool menu 470. In FIGS. 5 and 6, the selected brush tool 471 is used to paint the mask 440, such that the dark color position of a second image 420 at a second layer 421 corresponding to the mask 440 is set to a black color. If the user selects to apply a gentle pressure of the brush tool 471, the user needs to adjust the transparency of the black color, such that the image 410 (or foreground) at the first layer 411 is merged with the second image 420 (or background) at the second layer 421 to form a composed image 430 with the best composition effect.
From the description above, the image processing software available in the market can use the concept and technique of a layer to provide a tool for editing the image on each layer, or rearranging the image sequence of each layer, and can use the image composition technology to simulate a digital dark room, for editing and composing images, but these image processing software cannot show the effect of different vision models for the image.
As LMS is a color space used for indicating the response of three kinds of cones of human eyes, which refer to the sensitivity of color lights with a long wavelength, a medium wavelength and a short wavelength respectively, and the cross-section of a human retinal-cortical system includes complicated neural links. Only the LMS cone is known in general, but the profound structure of the retinal-cortical system still includes tree-structured constructions of cells strains, and the root of these constructions link several cones together to form a so-called “ganglion cell”, for making several receptive fields. Although neurophysists already have relatively high understanding on the visual imaging method of a retinal-cortical system of human eyes, yet this understanding is limited to an edge enhancement effect only, since the ganglion cells of different sizes are distributed increasingly denser from a fovea to the peripheral areas of a cornea, and thus the basic visual imaging principle decreases the vision from the center of the visual line to the peripheral areas. While human eyes are viewing a scene, an image sensed by a fixation point or a perceptual field of an eye cannot be the same as a camera or camcorder as shown in FIG. 7 for treating each position on the image 510 the same way. In fact, human eyes as shown in FIG. 8 only perceive an area (such as the cross area) interested to the eyes for a longer time, but the fixation point or perceptive field varies and the level of fixation is different. As a result, an image 530 with the effect of a different vision model can be produced in an imaging area of a human brain as shown in FIG. 9.
In recent years, unsharp-masking (USM) has been used extensively in different traditional image processing software and provided for users to perform special effects for an image. Regardless of the computation program used by these image processing software, the core technology uses the Laplacian of Gaussian edge enhancement technology and concept to simulate the effects of a receptive field of a human vision, but the computation carries out a single-level processing for the image only, and it cannot show the effect of different vision models for the image.